The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Multiple speed automatic transmissions are the overwhelming transmission choice for purchasers of passenger cars, sport utility vehicles and light trucks.
In such a typical automatic transmission, certain elements of a plurality of planetary gear assemblies are (1) interconnected by permanent coupling members, (2) selectively interconnected by friction clutches or (3) selectively grounded by brakes. Specific combinations of the clutches and brakes are engaged or activated in sequence to provide a predetermined sequence of numerically related gear ratios and thus output speeds and torques.
Increasingly demanding efficiency, performance and economic goals continue to encourage automatic transmission research and development. A result of this effort has been a steady increase in the number of available forward speeds or gear ratios in an automatic transmission. Whereas three, four or five speed automatic transmissions were once commonplace and considered to provide sufficient operating flexibility and performance, the industry and consumer preference has moved to six and eight speed automatic transmissions.
Because they so closely match the power and torque outputs of an engine to vehicle speed and load, six and eight speed automatic transmissions provide significant performance enhancements and fuel consumption reduction. Nonetheless, such transmissions are known to have drawbacks. Two known and related drawbacks are complexity and cost. Because of their benefits and in spite of their drawbacks, there is ongoing and increasing demand for automatic transmissions having more forward gears or speed ratios. The present invention provides an automatic transmission having nine, ten or eleven forward speeds or gear ratios and one which is both compact and relatively inexpensive.